Port wine stain (PWS) is a vascular malformation of human skin. Presently, all patients are treated using a single cryogen spurt (for epidermal protection) and single laser pulse exposure (SCS-SLP). However, PWS response remains unpredictable with less than 10% of patients achieving complete fading of their PWS after SCS-SLP. Inadequate PWS therapeutic outcome is a clinically significant problem that requires a solution. The central hypothesis of the proposed research is that multiple cryogen spurts (MCS) applied intermittently with multiple laser pulse (MLP) exposures (MCS-MLP) is not only safer than SCS- SLP but also expected to improve PWS therapeutic outcome. The proposed research addresses a critical barrier of inadequate PWS blood vessel heating. While MCS maintain the epidermal temperature well below the damage threshold, delivery of MLP increases the core intravascular PWS blood vessel temperature because of significant heat accumulation in the vessels with each successive laser pulse. Historically, MLP for PWS treatment involved the delivery of a series of laser pulses on the order of 1 Hz. The proposed research involves using MLP of much lower radiant exposure delivered at much higher repetition rates (~20 Hz) in combination with MCS. The proposed research also employs image-guided therapy to select the optimal laser treatment parameters on an individual patient basis after PWS lesion geometry has been characterized by infrared tomography (IRT). We expect that PWS treated using the MCS-MLP approach in conjunction with treatment parameters selected on an individual patient basis will have improved blanching responses. In preliminary studies conducted on PWS human skin, the feasibility and potential application of the MCS-MLP approach to cause destruction of subsurface PWS blood vessels in human skin, without damaging the overlying epidermis, has been demonstrated. The objective of the studies proposed herein is expected to lead to the development of a novel, high impact therapeutic approach as a solution for the long-standing problem of ineffective treatment of PWS. The research team is highly qualified by training and experience to accomplish the specific aims of this proposal. The team comprises expertise in medical laser therapy (Dr. Nelson), engineering (Drs. Svaasand and Jia), physics (Dr. Majaron) and physiology (Dr. Tan). PUBLIC HEALTH RELEVANCE: The current approach to the clinical management of patients with port wine stain (PWS) birthmarks is inadequate. The objective of the studies proposed herein using multiple cryogen spurts (MCS) applied intermittently with multiple laser pulse (MLP) exposures (MCS-MLP) is expected to lead to the development of a novel, high impact therapeutic approach as a solution for the long-standing problem of ineffective treatment of PWS. Such an outcome will contribute to the NIH mission of methodology development to improve fundamentally the treatment of disease.